If you have installed language module and mention your your template it must show in front office. So that you can change language.

Although you have installed language pack it will not be 100% translated in your desire language. It will install only core part of prestashop entire. And it is far better done by prestashop team and launage contributors.

There are still two section you need to translate on your own.

1. Module
2. Content

1. Module
Here, module stands for those design part which are fixed on template. Such as search box, block cart, slider, cms, contact info etc. If you feel it is not translated in your desire language . Please follow below instruction.

Click on localization > Translation

In “Modify translations ” fieldset section. You will see three option “Type of translation
, Select your theme, Select your language”. Here you need to choose “Front-office-translation“.
Select you current active theme from “Select your theme” option
At last select your desire language on which you are going to manually translate and then click on modify button on right side.

Now you will see numbers of modules to be translate in your desire language.

Once you complete manually translate. Again repeat action with selecting “Installed module translation” from “Type of translation” as you select “Front-office-translation” just before. Again translated manually for “Installed module translation”.

2. Content
Here content stands for content part which is dynamic and you can change on your own . Such as menu, product description, category name, product name. On every content part you will see and option to select language . So, that you can translate on your own manually.

Here, we have show category and product description page can be editable in different once you change language on side on each text box. Once you translated language on category name it will effect on your main menu.